refactor: extract tests from League.test.tsx into their own relevant test files

[Damon-Thomas]

All tests involving the league class are int eh League.test.tsx file. It is now over 1000 lines and getting hard to follow. Extract tests for each part into their own file and test the actual function instead of just that the class is getting the data.

• create new test files for appropriate units
• extract relevant tests from league
• create new tests for both functions and integration with league